The Death and Life of Great American Cities by Jane Jacobs. Anyone interested in understanding how cities work in everyday life should start here. Written by a Greenwich Village mother who used tools no more sophisticated than her eye and ear, the book turned the urban planning establishment upside down when it appeared in 1961. Widely regarded as the twentieth century's most important book on urbanism, it has never been out of print.
A Pattern Language: Towns, Buildings, Construction by Christopher Alexander et al. The authors explicate 253 "patterns" that can make our designed world work better, from the daylighting of rooms to the dimensions of porches to the arrangement of city blocks.
City Comforts: How to Build an Urban Village by David Sucher. An unpretentious, extensively illustrated book with a kitchen sink of small ideas on improving urban places. Some of the ideas could have used an editor (the book is self-published), but it's nonetheless worth looking into, especially for novices and nonprofessionals.
I've linked the titles above to Amazon so you can learn more about the books, but please buy them locally if at all possible.